How Milk Is Made

How is breast milk made?

Many mothers find they can appreciate their babies' breastfeeding patterns or the need for frequent feedings when they understand how breast milk is produced. Initially, hormones play a greater role. After the first one or two weeks postpartum (after the baby is born), milk removal has a greater effect on the amount of milk produced.

With the expulsion of the placenta after a baby's birth, a drop in the hormones that maintained the pregnancy soon occurs and allows the hormone prolactin to begin to work. Prolactin "tells" the breasts it is time to begin producing large amounts of milk. A mother feels the result of prolactin when her milk "comes in" at around three to five days postpartum. Increased milk production usually occurs at this time even if a baby has not been breastfeeding well or often. However, frequent breastfeeding sometimes speeds up the process of establishing increased milk production. Occasionally, a mother experiences a delay in the production of large amounts of milk.

How much milk is needed?

Ongoing, long-term milk production depends mostly on milk removal. The more often milk is removed and the more completely it is removed, the more milk the breasts make. The opposite is also true. When milk is removed less often or an insufficient amount is removed, the breasts get the signal to slow milk production and make less. Milk removal occurs when a baby effectively breastfeeds.

Effective breastfeeding requires effective sucking by the baby so that enough milk is transferred from the breast into the baby's mouth where it is swallowed. To suck effectively, a baby must latch deeply onto the breast and use the structures in his/her mouth to create intermittent (periodic) suction and also compress the milk sinuses (enlarged area of milk ducts) lying beneath the areola -- the area about 1½ to 2 inches behind the nipple tip. Proper sucking signals the mother's body to release the hormone oxytocin, which results in a greater transfer of milk with the milk-ejection reflex (MER), or milk "let down."

If a baby is not breastfeeding effectively, milk transfer also can be accomplished through milk expression techniques. When using manual expression, a mother compresses the milk sinuses by hand to remove milk. Breast pumps remove milk by creating suction, and a few also have features that compress milk sinuses to some degree. Generally, the milk-ejection reflex is triggered during milk expression sessions, especially if frequent and regular sessions occur.